Asphalt-containing, waste products are normally disposed of at the present time as landfill. However land suitable for landfill purposes is becoming harder to find and landfill costs are rising. Also, asphalt-containing, waste products are a potential fire hazard in landfill sites and pollute the atmosphere when burning. The asphalt itself in the waste products is also becoming too valuable a commodity to throw away.
It had been proposed to recycle the asphalt-containing, waste products to recover the asphalt and also other components of the products. However the known methods are not very economical. Most of the known methods try to recover the asphalt in pure form and the methods used are quite expensive. It is known, for example, as shown in U.S. Pat. No. 4,222,851 to dry grind waste asphalt shingles and to treat the ground particles with solvent to dissolve the asphalt and to then recover the pure asphalt by evaporation. The other shingle components such as fibers and rock granules are also separated and recovered. This method involves a number of steps and is quite complicated and expensive.
U.S. Pat. No. 4,269,693 discloses grinding a waste asphalt product at a cool temperature and then using a flotation step to separate lighter particles including asphalt from heavier particles. The lighter particles are then melted and filtered to obtain pure asphalt. Again many steps are employed asking the method expensive.
U.S. Pat. No. 4,706,893 discloses the dry grinding of waste asphalt shingles into asphalt containing particles and directly incorporating the dry waste particles into the making of a new asphalt product. This method is quite cheap but is only suitable for use with an asphalt plant which heats asphalt and mixes it with granules.